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<table width="100%" summary="page for NOxEmissions"><tr><td>NOxEmissions</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>NOx Air Pollution Data</h2>

<h3>Description</h3>

<p>A typical medium sized environmental data set with hourly measurements
of <i>NOx</i> pollution content in the ambient air.
</p>


<h3>Usage</h3>

<pre>data(NOxEmissions, package="robustbase")</pre>


<h3>Format</h3>

<p>A data frame with 8088 observations on the following 4 variables.
</p>

<dl>
<dt><code>julday</code></dt><dd><p>day number, a factor with levels <code>373</code>
... <code>730</code>, typically with 24 hourly measurements.</p>
</dd>
<dt><code>LNOx</code></dt><dd><p><i>\log</i> of hourly mean of NOx concentration in
ambient air [ppb] next to a highly frequented motorway.</p>
</dd>
<dt><code>LNOxEm</code></dt><dd><p><i>\log</i> of hourly sum of NOx emission of
cars on this motorway in arbitrary units.</p>
</dd>
<dt><code>sqrtWS</code></dt><dd><p>Square root of wind speed [m/s].</p>
</dd>
</dl>



<h3>Details</h3>

<p>The original data set had more observations, but with missing values.
Here, all cases with missing values were omitted
(<code>na.omit(.)</code>), and then only those were retained that
belonged to days with at least 20 (fully) observed hourly
measurements.
</p>


<h3>Source</h3>

<p>René Locher (at ZHAW, Switzerland).

</p>


<h3>See Also</h3>

<p>another NOx dataset, <code>ambientNOxCH</code>.
</p>


<h3>Examples</h3>

<pre>
data(NOxEmissions)
plot(LNOx ~ LNOxEm, data = NOxEmissions, cex = 0.25, col = "gray30")

## Not run: ## these take too much time --
 ## p = 340  ==&gt; already Least Squares is not fast
 (lmNOx &lt;- lm(LNOx ~ . ,data = NOxEmissions))
 plot(lmNOx) #-&gt;  indication of 1 outlier

 M.NOx &lt;- MASS::rlm(LNOx ~ . , data = NOxEmissions)
 ## M-estimation works
 ## whereas  MM-estimation fails:
 try(MM.NOx &lt;- MASS::rlm(LNOx ~ . , data = NOxEmissions, method = "MM"))
 ## namely because S-estimation fails:
 try(lts.NOx &lt;- ltsReg(LNOx ~ . , data = NOxEmissions))
 try(lmR.NOx &lt;- lmrob (LNOx ~ . , data = NOxEmissions))

## End(Not run)
</pre>


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